Partial support is requested for the 2002 Gordon Research Conference Muscle: Contractile Proteins to bring together biophysicists, biochemists, cell biologists and physiologists to address the mechanism of muscle contraction and its regulation. While the actin myosin contractile system has been the most extensively studied, it is now well recognized that acto myosin based systems have fundamental roles in many cellular activities ranging from organelle transport to cell division. The overall focus of the conference will be the Molecular Basis of Muscle Contraction. Although skeletal muscle contraction has been the primary focus of this conference in the past, a significant database is now being generated through studies of other muscle and nonmuscle contractile systems. Therefore, a comparative approach will be emphasized at this conference by having presentations and discussions by scientists who study many different members of the myosin superfamily as well as other molecular motors (e.g. kinesin). It is anticipated that scientists in the muscle community will benefit from the insights gained by understanding the range of functional capacities that myosin may exhibit in other motile systems. There are two major aims. One is to discuss important recent developments in the field ranging from newly determined molecular structures to single molecule studies in solution and in fibers as they relate to the contractile mechanism. In the past decade the availability of atomic resolution structures for actin and myosin, techniques for studying single molecules, improved EM imaging methods, and the opportunity to study genetically modified molecules have revolutionized the study of the contractile process. The questions, models, and underlying assumptions, predate these newer developments. The second aim of the conference is to focus on the major questions, models and controversial issues in light of recent results in discussion based workshops. There will be nine sessions in which there will be a small number of formal presentations followed by a discussion workshop on critical issues relating to the session. The discussions will be led by the Session Chair and a Session Poster Chair who will together be responsible for incorporating the poster participants into the discussion.